1 | /* Specialized bits of code needed to support construction and |
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2 | destruction of file-scope objects in C++ code. |
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3 | |
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4 | Written by Ron Guilmette (rfg@netcom.com) with help from Richard Stallman. |
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5 | |
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6 | Copyright (C) 1991, 1994, 1995 Free Software Foundation, Inc. |
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7 | |
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8 | This file is part of GNU CC. |
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9 | |
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10 | GNU CC is free software; you can redistribute it and/or modify |
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11 | it under the terms of the GNU General Public License as published by |
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12 | the Free Software Foundation; either version 2, or (at your option) |
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13 | any later version. |
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14 | |
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15 | GNU CC is distributed in the hope that it will be useful, |
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16 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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17 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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18 | GNU General Public License for more details. |
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19 | |
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20 | You should have received a copy of the GNU General Public License |
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21 | along with GNU CC; see the file COPYING. If not, write to |
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22 | the Free Software Foundation, 59 Temple Place - Suite 330, |
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23 | Boston, MA 02111-1307, USA. */ |
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24 | |
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25 | /* As a special exception, if you link this library with files |
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26 | compiled with GCC to produce an executable, this does not cause |
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27 | the resulting executable to be covered by the GNU General Public License. |
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28 | This exception does not however invalidate any other reasons why |
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29 | the executable file might be covered by the GNU General Public License. */ |
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30 | |
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31 | /* This file is a bit like libgcc1.c/libgcc2.c in that it is compiled |
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32 | multiple times and yields multiple .o files. |
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33 | |
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34 | This file is useful on target machines where the object file format |
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35 | supports multiple "user-defined" sections (e.g. COFF, ELF, ROSE). On |
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36 | such systems, this file allows us to avoid running collect (or any |
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37 | other such slow and painful kludge). Additionally, if the target |
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38 | system supports a .init section, this file allows us to support the |
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39 | linking of C++ code with a non-C++ main program. |
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40 | |
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41 | Note that if INIT_SECTION_ASM_OP is defined in the tm.h file, then |
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42 | this file *will* make use of the .init section. If that symbol is |
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43 | not defined however, then the .init section will not be used. |
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44 | |
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45 | Currently, only ELF and COFF are supported. It is likely however that |
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46 | ROSE could also be supported, if someone was willing to do the work to |
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47 | make whatever (small?) adaptations are needed. (Some work may be |
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48 | needed on the ROSE assembler and linker also.) |
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49 | |
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50 | This file must be compiled with gcc. */ |
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51 | |
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52 | /* It is incorrect to include config.h here, because this file is being |
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53 | compiled for the target, and hence definitions concerning only the host |
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54 | do not apply. */ |
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55 | |
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56 | #include "tm.h" |
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57 | |
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58 | /* Provide default definitions for the pseudo-ops used to switch to the |
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59 | .ctors and .dtors sections. |
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60 | |
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61 | Note that we want to give these sections the SHF_WRITE attribute |
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62 | because these sections will actually contain data (i.e. tables of |
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63 | addresses of functions in the current root executable or shared library |
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64 | file) and, in the case of a shared library, the relocatable addresses |
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65 | will have to be properly resolved/relocated (and then written into) by |
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66 | the dynamic linker when it actually attaches the given shared library |
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67 | to the executing process. (Note that on SVR4, you may wish to use the |
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68 | `-z text' option to the ELF linker, when building a shared library, as |
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69 | an additional check that you are doing everything right. But if you do |
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70 | use the `-z text' option when building a shared library, you will get |
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71 | errors unless the .ctors and .dtors sections are marked as writable |
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72 | via the SHF_WRITE attribute.) */ |
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73 | |
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74 | #ifndef CTORS_SECTION_ASM_OP |
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75 | #define CTORS_SECTION_ASM_OP ".section\t.ctors,\"aw\"" |
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76 | #endif |
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77 | #ifndef DTORS_SECTION_ASM_OP |
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78 | #define DTORS_SECTION_ASM_OP ".section\t.dtors,\"aw\"" |
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79 | #endif |
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80 | |
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81 | #ifdef OBJECT_FORMAT_ELF |
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82 | |
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83 | /* Declare a pointer to void function type. */ |
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84 | typedef void (*func_ptr) (void); |
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85 | #define STATIC static |
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86 | |
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87 | #else /* OBJECT_FORMAT_ELF */ |
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88 | |
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89 | #include "gbl-ctors.h" |
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90 | |
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91 | #ifndef ON_EXIT |
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92 | #define ON_EXIT(a, b) |
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93 | #endif |
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94 | #define STATIC |
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95 | |
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96 | #endif /* OBJECT_FORMAT_ELF */ |
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97 | |
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98 | #ifdef CRT_BEGIN |
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99 | |
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100 | #ifdef INIT_SECTION_ASM_OP |
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101 | |
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102 | #ifdef OBJECT_FORMAT_ELF |
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103 | |
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104 | /* Run all the global destructors on exit from the program. */ |
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105 | |
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106 | /* Some systems place the number of pointers in the first word of the |
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107 | table. On SVR4 however, that word is -1. In all cases, the table is |
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108 | null-terminated. On SVR4, we start from the beginning of the list and |
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109 | invoke each per-compilation-unit destructor routine in order |
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110 | until we find that null. |
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111 | |
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112 | Note that this function MUST be static. There will be one of these |
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113 | functions in each root executable and one in each shared library, but |
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114 | although they all have the same code, each one is unique in that it |
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115 | refers to one particular associated `__DTOR_LIST__' which belongs to the |
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116 | same particular root executable or shared library file. */ |
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117 | |
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118 | static func_ptr __DTOR_LIST__[]; |
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119 | static void |
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120 | __do_global_dtors_aux () |
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121 | { |
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122 | func_ptr *p; |
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123 | for (p = __DTOR_LIST__ + 1; *p; p++) |
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124 | (*p) (); |
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125 | } |
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126 | |
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127 | /* Stick a call to __do_global_dtors_aux into the .fini section. */ |
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128 | static void |
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129 | fini_dummy () |
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130 | { |
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131 | asm (FINI_SECTION_ASM_OP); |
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132 | __do_global_dtors_aux (); |
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133 | #ifdef FORCE_FINI_SECTION_ALIGN |
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134 | FORCE_FINI_SECTION_ALIGN; |
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135 | #endif |
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136 | asm (TEXT_SECTION_ASM_OP); |
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137 | } |
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138 | |
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139 | #else /* OBJECT_FORMAT_ELF */ |
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140 | |
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141 | /* The function __do_global_ctors_aux is compiled twice (once in crtbegin.o |
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142 | and once in crtend.o). It must be declared static to avoid a link |
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143 | error. Here, we define __do_global_ctors as an externally callable |
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144 | function. It is externally callable so that __main can invoke it when |
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145 | INVOKE__main is defined. This has the additional effect of forcing cc1 |
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146 | to switch to the .text section. */ |
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147 | static void __do_global_ctors_aux (); |
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148 | void __do_global_ctors () |
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149 | { |
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150 | #ifdef INVOKE__main /* If __main won't actually call __do_global_ctors |
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151 | then it doesn't matter what's inside the function. |
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152 | The inside of __do_global_ctors_aux is called |
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153 | automatically in that case. |
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154 | And the Alliant fx2800 linker crashes |
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155 | on this reference. So prevent the crash. */ |
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156 | __do_global_ctors_aux (); |
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157 | #endif |
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158 | } |
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159 | |
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160 | asm (INIT_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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161 | |
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162 | /* On some svr4 systems, the initial .init section preamble code provided in |
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163 | crti.o may do something, such as bump the stack, which we have to |
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164 | undo before we reach the function prologue code for __do_global_ctors |
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165 | (directly below). For such systems, define the macro INIT_SECTION_PREAMBLE |
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166 | to expand into the code needed to undo the actions of the crti.o file. */ |
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167 | |
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168 | #ifdef INIT_SECTION_PREAMBLE |
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169 | INIT_SECTION_PREAMBLE; |
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170 | #endif |
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171 | |
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172 | /* A routine to invoke all of the global constructors upon entry to the |
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173 | program. We put this into the .init section (for systems that have |
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174 | such a thing) so that we can properly perform the construction of |
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175 | file-scope static-storage C++ objects within shared libraries. */ |
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176 | |
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177 | static void |
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178 | __do_global_ctors_aux () /* prologue goes in .init section */ |
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179 | { |
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180 | #ifdef FORCE_INIT_SECTION_ALIGN |
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181 | FORCE_INIT_SECTION_ALIGN; /* Explicit align before switch to .text */ |
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182 | #endif |
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183 | asm (TEXT_SECTION_ASM_OP); /* don't put epilogue and body in .init */ |
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184 | DO_GLOBAL_CTORS_BODY; |
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185 | ON_EXIT (__do_global_dtors, 0); |
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186 | } |
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187 | |
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188 | #endif /* OBJECT_FORMAT_ELF */ |
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189 | #endif /* defined(INIT_SECTION_ASM_OP) */ |
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190 | |
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191 | /* Force cc1 to switch to .data section. */ |
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192 | static func_ptr force_to_data[0] = { }; |
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193 | |
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194 | /* NOTE: In order to be able to support SVR4 shared libraries, we arrange |
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195 | to have one set of symbols { __CTOR_LIST__, __DTOR_LIST__, __CTOR_END__, |
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196 | __DTOR_END__ } per root executable and also one set of these symbols |
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197 | per shared library. So in any given whole process image, we may have |
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198 | multiple definitions of each of these symbols. In order to prevent |
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199 | these definitions from conflicting with one another, and in order to |
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200 | ensure that the proper lists are used for the initialization/finalization |
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201 | of each individual shared library (respectively), we give these symbols |
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202 | only internal (i.e. `static') linkage, and we also make it a point to |
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203 | refer to only the __CTOR_END__ symbol in crtend.o and the __DTOR_LIST__ |
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204 | symbol in crtbegin.o, where they are defined. */ |
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205 | |
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206 | /* The -1 is a flag to __do_global_[cd]tors |
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207 | indicating that this table does not start with a count of elements. */ |
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208 | #ifdef CTOR_LIST_BEGIN |
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209 | CTOR_LIST_BEGIN; |
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210 | #else |
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211 | asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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212 | STATIC func_ptr __CTOR_LIST__[1] = { (func_ptr) (-1) }; |
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213 | #endif |
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214 | |
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215 | #ifdef DTOR_LIST_BEGIN |
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216 | DTOR_LIST_BEGIN; |
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217 | #else |
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218 | asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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219 | STATIC func_ptr __DTOR_LIST__[1] = { (func_ptr) (-1) }; |
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220 | #endif |
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221 | |
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222 | #endif /* defined(CRT_BEGIN) */ |
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223 | |
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224 | #ifdef CRT_END |
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225 | |
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226 | #ifdef INIT_SECTION_ASM_OP |
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227 | |
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228 | #ifdef OBJECT_FORMAT_ELF |
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229 | |
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230 | static func_ptr __CTOR_END__[]; |
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231 | static void |
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232 | __do_global_ctors_aux () |
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233 | { |
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234 | func_ptr *p; |
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235 | for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--) |
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236 | (*p) (); |
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237 | } |
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238 | |
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239 | /* Stick a call to __do_global_ctors_aux into the .init section. */ |
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240 | static void |
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241 | init_dummy () |
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242 | { |
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243 | asm (INIT_SECTION_ASM_OP); |
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244 | __do_global_ctors_aux (); |
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245 | #ifdef FORCE_INIT_SECTION_ALIGN |
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246 | FORCE_INIT_SECTION_ALIGN; |
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247 | #endif |
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248 | asm (TEXT_SECTION_ASM_OP); |
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249 | |
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250 | /* This is a kludge. The Linux dynamic linker needs ___brk_addr, __environ |
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251 | and atexit (). We have to make sure they are in the .dynsym section. We |
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252 | accomplish it by making a dummy call here. This |
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253 | code is never reached. */ |
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254 | |
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255 | #if defined(__linux__) && defined(__PIC__) |
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256 | { |
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257 | extern void *___brk_addr; |
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258 | extern char **__environ; |
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259 | |
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260 | ___brk_addr = __environ; |
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261 | atexit (); |
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262 | } |
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263 | #endif |
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264 | } |
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265 | |
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266 | #else /* OBJECT_FORMAT_ELF */ |
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267 | |
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268 | /* Stick the real initialization code, followed by a normal sort of |
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269 | function epilogue at the very end of the .init section for this |
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270 | entire root executable file or for this entire shared library file. |
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271 | |
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272 | Note that we use some tricks here to get *just* the body and just |
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273 | a function epilogue (but no function prologue) into the .init |
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274 | section of the crtend.o file. Specifically, we switch to the .text |
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275 | section, start to define a function, and then we switch to the .init |
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276 | section just before the body code. |
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277 | |
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278 | Earlier on, we put the corresponding function prologue into the .init |
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279 | section of the crtbegin.o file (which will be linked in first). |
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280 | |
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281 | Note that we want to invoke all constructors for C++ file-scope static- |
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282 | storage objects AFTER any other possible initialization actions which |
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283 | may be performed by the code in the .init section contributions made by |
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284 | other libraries, etc. That's because those other initializations may |
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285 | include setup operations for very primitive things (e.g. initializing |
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286 | the state of the floating-point coprocessor, etc.) which should be done |
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287 | before we start to execute any of the user's code. */ |
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288 | |
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289 | static void |
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290 | __do_global_ctors_aux () /* prologue goes in .text section */ |
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291 | { |
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292 | asm (INIT_SECTION_ASM_OP); |
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293 | DO_GLOBAL_CTORS_BODY; |
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294 | ON_EXIT (__do_global_dtors, 0); |
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295 | } /* epilogue and body go in .init section */ |
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296 | |
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297 | #endif /* OBJECT_FORMAT_ELF */ |
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298 | |
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299 | #endif /* defined(INIT_SECTION_ASM_OP) */ |
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300 | |
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301 | /* Force cc1 to switch to .data section. */ |
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302 | static func_ptr force_to_data[0] = { }; |
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303 | |
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304 | /* Put a word containing zero at the end of each of our two lists of function |
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305 | addresses. Note that the words defined here go into the .ctors and .dtors |
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306 | sections of the crtend.o file, and since that file is always linked in |
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307 | last, these words naturally end up at the very ends of the two lists |
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308 | contained in these two sections. */ |
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309 | |
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310 | #ifdef CTOR_LIST_END |
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311 | CTOR_LIST_END; |
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312 | #else |
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313 | asm (CTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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314 | STATIC func_ptr __CTOR_END__[1] = { (func_ptr) 0 }; |
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315 | #endif |
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316 | |
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317 | #ifdef DTOR_LIST_END |
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318 | DTOR_LIST_END; |
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319 | #else |
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320 | asm (DTORS_SECTION_ASM_OP); /* cc1 doesn't know that we are switching! */ |
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321 | STATIC func_ptr __DTOR_END__[1] = { (func_ptr) 0 }; |
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322 | #endif |
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323 | |
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324 | #endif /* defined(CRT_END) */ |
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